Re: [PATCH 4.19 009/191] KVM: nVMX: Use correct root level for nested EPT shadow page tables

Hi!

Hardcode the EPT page-walk level for L2 to be 4 levels, as KVM's MMU currently also hardcodes the page walk level for nested EPT to be 4 levels. The L2 guest is all but guaranteed to soft hang on its first instruction when L1 is using EPT, as KVM will construct 4-level page tables and then tell hardware to use 5-level page tables.

I don't get it. 7/191 reverts the patch, then 9/191 reverts the revert. Can we simply drop both 7 and 9, for exactly the same result?

(Patch 8 is a unused file, so it does not change the picture).

Best regards, Pavel

+++ b/arch/x86/kvm/vmx.c @@ -5302,6 +5302,9 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) static int get_ept_level(struct kvm_vcpu *vcpu) {

• /* Nested EPT currently only supports 4-level walks. */
• if (is_guest_mode(vcpu) && nested_cpu_has_ept(get_vmcs12(vcpu)))

• return 4;
  

  if (cpu_has_vmx_ept_5levels() && (cpuid_maxphyaddr(vcpu) > 48)) return 5; return 4;

-- 2.20.1